Radiological imaging is recognized to have significant value for the dental practitioner, helping to identify various problems and to validate other measurements and observations related to the patient's teeth and supporting structures. Among x-ray systems with particular promise for improving dental care is the extra-oral imaging apparatus that is capable of obtaining a contiguous panoramic radiograph of the patient showing the entire dentition of the jaw. To obtain this type of image, a radiation source and an imaging detector, maintained at a fixed distance from each other, synchronously revolve about the patient, taking a series of images by directing and detecting radiation that is directed through the patient at different angles of revolution.
Combination systems that provide both CT and panoramic x-ray imaging have been proposed. For example, U.S. Pat. No. 6,118,842 entitled “X-RAY IMAGING APPARATUS” to Arai et al. describes an X-ray imaging apparatus for both CT imaging and panoramic imaging. The apparatus includes an X-ray source, an X-ray detector for detecting X-rays having passed through the subject, and supporting means for supporting the X-ray source and the X-ray detector so that they are spatially opposed to each other across the subject; and mode switching means for switching between a CT mode and a panorama mode. To detect X-rays, one large area X-ray detector is used. The X-ray imaging apparatus can obtain both types of images by switching modes during the imaging session. However, the proposed imaging apparatus performs both CT and panoramic imaging using only one detector. This requires an expensive detector capable of carrying out both imaging functions in a satisfactory manner.
More recently, U.S. Pat. No. 7,236,563 entitled “COMBINED PANORAMIC AND COMPUTED TOMOGRAPHY PHOTOGRAPHING APPARATUS” to Sa et al. describes a combination system that allows both CT and panoramic imaging using two separate sensors or detectors. By way of example, FIG. 1 in the present application shows an embodiment of the Sa et al. '563 imaging system, a combined panoramic and CT imaging apparatus 40. A telescopic column 18 is adjustable for height of the subject. The patient 12 or other subject, shown in dotted outline, is positioned between an x-ray source 10 and an x-ray imaging sensor panel 20. X-ray imaging sensor panel 20 rotates on a rotatable mount 30 in order to position either a CT or a panoramic sensor 21 for obtaining the exposure. For CT imaging, CT sensor 21 is positioned behind the subject, relative to x-ray source 10. The operator rotates CT sensor 21 into this position as part of imaging setup. Similarly, the operator rotates panoramic sensor 21 into position behind the subject as part of the setup for a panoramic imaging session.
Another system combines CT, panoramic, and cephalometric imaging from a single apparatus. U.S. Pat. No. 7,424,091 entitled “COMBINED PANORAMIC, CT (COMPUTED TOMOGRAPHY) AND CEPHALOMETRIC PHOTOGRAPHING APPARATUS” to Park et al. describes such a system.
One problem common to such systems for extra-oral imaging relates to the need both to keep the subject motionless and to maintain the subject in exactly the same position for each image capture during the imaging session. The perspective view of FIG. 2 shows one type of patient stabilization apparatus in an extra-oral imaging apparatus 50 that is typical of such systems. A handle 52 is mounted on column 18, giving the patient a place to grip for steadily maintaining a position. A chin rest 54 provides a bite element 56 and guides 58 for holding the head still while x-ray source 10 and sensor panel 20 revolve about the patient.
While conventional solutions such as that shown in FIG. 2 have the supporting structures that perform the needed task of keeping the patient still and in a fixed position, however, there is room for improvement. One difficulty relates to the job of initial setup, placing the patient in position, with the proper settings for chin rest height, bite element position, and handle height. The technician must work from behind the patient for much of this adjustment with reduced visibility, having little room to see how the patient is situated. Further, the patient may rock forward or backward on the chin, even with the guiding and bite devices provided.
Still other problems with conventional solutions relate to setting the imaging apparatus to the proper height for the patient and supporting the patient's head at an appropriate angle for CBCT imaging. Conventional systems use a number of complex height detection and head alignment sensing devices, including low-power lasers for example, for achieving proper positioning of the apparatus relative to the patient's head and for positioning the head at a suitable angle. Complex sensing and detection systems of this type can be costly and difficult to implement, further complicating the job of the technician or practitioner.
Another difficulty relates to patient comfort. With the arrangement of FIG. 2, the patient must stand facing away from the dentist or technician. Patients report feeling trapped and uncomfortable with such an apparatus, as if locked in place during the imaging session.
Thus, there is a need for a patient support apparatus that allows easier setup by the technician and is less confining and intimidating to the patient.